This invention relates generally to the field of devices useful in protecting animals against arthropod pests. The invention relates more specifically to collar and ear tag devices capable of the controlled, sustained release of an effective amount of an active ingredient that can protect an animal against arthropod pests, wherein the active ingredient is part of an improved gel formulation contained within such devices.
Various methods have been employed to protect animals against arthropod pests, particularly fleas, ticks, flies, and mites. Customarily, animals have been sprayed with or dipped in an insecticide solution. However, this type of treatment provides only temporary protection, usually lasting less than three weeks as the result of degradation by various environmental factors such as sunlight, moisture, etc.
Attempts to improve and simplify the control of arthropod pests have previously involved providing a device, such as a collar or ear tag comprising an insecticide, to be worr by the animal. For domesticated pets such as dogs and cats, insecticidal collars have beer used which comprise a solid matrix material impregnated with an insecticidal composition that is released from the collar and spread when the collar rubs against the animal""s coat. Ear tags, which have been used in an attempt to control arthropod pests of livestock, also comprise a solid matrix material impregnated with an insecticidal composition that is released and spread when the tag rubs against the animal""s coat. However, the protection offered by such collar and ear tag devices is unreliable and short-lived, partially because the solid matrix material is inefficient at releasing the insecticidal composition.
U.S. Pat. No. 5,660,844 to Christie et al. refers to collar and ear tag devices to protect animals against arthropod infestation, which devices comprise a gel enclosed in a cavity inside a reservoir. The gel referred to includes a combination of a wax gelling agent, an organic solvent such as mineral oil, and an insecticidal composition. These devices are generally more effective and provide longer lasting protection than prior devices and methods However, as much as three to five weeks are required for an effective amount of the active ingredient to permeate through the wall of the reservoir after manufacture. In addition, a gel that comprises mineral oil can leave an oily deposit on the animal""s coat. Furthermore, mineral oil is known to irritate the skin of some animals. Still further, contamination of the open ends of the tube of the reservoir with such a gel often inhibits the tube from being adequately sealed during manufacture. Still further, certain insecticides such as cypermethrin are not miscible in such a gel.
A need therefore exists for collar and ear tag devices comprising an improved gel formulation that requires a shorter time period for an effective amount of the active ingredient to permeate through the wall of the reservoir after manufacture, that does not leave an oily residue on the animal""s coat or irritate the skin, that does not inhibit the sealing of the reservoir, and in which insecticides such as cypermethrin are miscible.
In one aspect, the present invention provides a device capable of the controlled, sustained release of an effective amount of an active ingredient that can protect an animal against arthropod pests such as fleas, ticks, flies, and mites. The device comprises a reservoir having a supporting membrane comprising an outside surface, and an inside surface defining an enclosed cavity, and a gel contained within the enclosed cavity and in contact with the inside surface, said gel comprising the admixture of a gelling agent which is a fatty acid or salt thereof, an organic solvent which is a linear aliphatic ester, a silicone-based fluid, or a combination thereof, and an active ingredient dispersed therein that can protect the animal against one or more arthropod pests, wherein the supporting membrane of the reservoir comprises a polymeric material that is permeable to the active ingredient. In a preferred though non-limiting embodiment, the supporting membrane of the reservoir is polyvinyl chloride (PVC), the fatty acid is stearic acid, the organic solvent is a combination of methyl palmitate and a silicone-based fluid such as dimethicone, and the active ingredient is an insecticide, an insect repellant, or an insect growth regulator (IGR), or a combination thereof. In a further preferred embodiment, the weight ratio of methyl palmitate and dimethicone in the organic solvent is about 50 weight % (wt %) methyl palmitate and about 50 wt % dimethicone In a particularly useful embodiment, the gel comprises from about 45 wt % to about 55 wt % stearic acid, from about 15 wt % to about 25 wt % organic solvent, and from about 18 wt % to about 28 wt % active ingredient. The gel can further comprise one or more additional components, including stabilizers such as anti-oxidants or ultraviolet light blockers, as needed. The device of the present invention is preferably in the form of a collar or ear tag which further comprises a fastening means for fastening the device around the neck or to the ear, respectively, of the animal.
In still another aspect, the present invention provides a gel in an improved formulation for use in a collar or ear tag device to protect an animal against arthropod pests, which gel comprises the admixture of a gelling agent which is a fatty acid or salt thereof, an organic solvent which is a linear aliphatic ester, a silicone-based fluid, or a combination thereof, and an active ingredient dispersed therein that can protect the animal against one or more arthropod pests.
In still another aspect, the present invention provides a method of preparing a device capable of the controlled, sustained release of an effective amount of an active ingredient that can protect an animal against arthropod pests, which device comprises a reservoir having a supporting membrane comprising an outside surface, and an inside surface defining an enclosed cavity, and a gel contained within the enclosed cavity and in contact with the inside surface, said gel comprising the admixture of a gelling agent which is a fatty acid or salt thereof, an organic solvent which is a linear aliphatic ester, a silicone-based fluid, or a combination thereof, and an active ingredient dispersed therein that can protect the animal against one or more arthropod pests, wherein the supporting membrane of the reservoir comprises a polymeric material that is permeable to the active ingredient, which method comprises filling a cavity defined by the inside surface of the supporting membrane with the gel and sealing the supporting membrane so as to enclose the gel in the cavity.
In still another aspect, the present invention provides a method of protecting animals against arthropod pests, comprising the step of fastening the device of the present invention, e.g., as a collar or ear tag, to the animal.